<template>
  <div>
    <router-link
      tag="div"
      to="/"
      class="header-abs"
      v-show="showAbs"
    >
      <div class="iconfont back-ground">&#xe624;</div>
    </router-link>
    <div class="header-fixed"
         v-show="!showAbs"
         :style="opacityStyle"
    >
      <div class="header">
        <router-link to="/">
          <div class="iconfont header-fixed-back">&#xe624;</div>
        </router-link>
        景点详情
      </div>
    </div>
  </div>
</template>

<script>
  export default {
    name: "Header",
    data(){
      return {
        showAbs : true,
        opacityStyle:{
          opacity: 0
        }
      }
    },
    methods:{
      handleScroll(){
        const top = document.documentElement.scrollTop
        if(top > 60){
          //  在滑动60~140之间的时候，让透明度有个过渡动画
          let opacity = top / 140
          opacity = opacity > 1 ? 1 : opacity
          this.opacityStyle = { opacity }
          this.showAbs = false
        }else {
          this.showAbs= true
        }
      }
    },
    activated() {
      window.addEventListener('scroll',this.handleScroll)
    },
    //  解绑scroll，以免对全局scroll造成影响
    deactivated() {
      window.removeEventListener('scroll',this.handleScroll)
    }
  }
</script>

<style lang="stylus" scoped>
  @import "~styles/varible.styl"
  .header-abs
    position: absolute
    left: .2rem
    top: .2rem
    width: .8rem
    height: .8rem
    text-align: center
    line-height: .8rem
    border-radius: .4rem
    background: rgb(0, 0, 0, .8)

    .back-ground
      color: #ffffff
      font-size: .4rem

  .header-fixed
    position: fixed
    top: 0
    left: 0
    right: 0
    height: .86rem
    line-height: .86rem
    text-align: center
    color: #fff
    background-color: $bgColor
    font-size: .32rem

    .header-fixed-back
      position: absolute
      top: 0
      left: 0
      width: .64rem
      text-align: center
      font-size: .4rem
      color: #fff
</style>
